This invention relates to push-in wire connectors. Push-in connectors operate, as the name implies, by simply pushing a stripped end of two or more wires or conductors into the connector. Once the wires are pushed into the connector no closing, crimping, twisting, insulation displacement or other manipulation of the connector is required to finish the connection, making the push-in connector advantageous from the standpoint of time needed to install it. The push-in connector must perform several tasks including electrically isolating its conductors from the surrounding environment, retaining the conductors in the connector, and providing good electrical conductivity between the conductors.
The electrical isolation function is typically performed by a housing made of electrically insulating material. The housing has a generally hollow interior. Openings in the housing provide access to the interior for the stripped ends of two or more electrical conductors. Once inside the housing the bared ends of the conductors are fully surrounded by the insulating housing.
The function of providing electrical conductivity is performed by an electrically-conductive shorting member. The shorting member, often called a busbar, is inside the housing and is disposed so as to be engageable with all conductors inserted into the housing. The shorting member provides a conductive path between all inserted conductors. Since the primary job of the busbar is conduction, it is typically made of a highly conductive material such as copper or tin-plated copper. But even a highly conductive busbar will not provide good conductivity between conductors if those conductors are not held firmly in contact with the busbar. Thus it is common to include a spring member which works in concert with the busbar to hold the conductors firmly against the busbar. Various arrangements of the spring member are possible, including building it into the housing, building it into the busbar, or making it a separate component in the interior of the housing. In any case, the spring member urges all conductors into solid mechanical and electrical engagement with the shorting member.
The function of holding the conductors in the housing is performed by a retention member that engages the ends of the inserted conductors and prevents axial retraction from the housing. As in the case of the spring member, the retention member could be built into the housing. Alternately, the retention member and spring member can be configured as a combined unit inside the housing. In either case the retention member grasps the conductors and prevents unintentional removal of the conductors from the housing. In some embodiments the retention member is releasable so that conductors may be selectively removed from the housing without damage to any of the components. In other embodiments where it is desired that the conductors not be removed from the connector under any circumstances the retention member is intentionally made to be non-releasable.
As just mentioned, the retention member is often configured in combination with the spring member to apply a force that urges the inserted conductor into contact with the shorting member and prevents retraction of the conductor. A common configuration is to have a resilient metal retention member having spring fingers formed therein. As a conductor is inserted into the housing it engages a spring finger and causes it to flex away from its rest position. The resulting deflection of the spring finger generates a compressive force on the conductor that presses it into solid contact with the busbar. The spring fingered is angled to permit insertion of the conductor past the finger in one direction but withdrawal of the conductor in the opposite direction is not permitted due to the self-locking configuration of the spring finger. Thus, engagement of the spring finger with the conductor provides the dual functions of pressing the conductor into the busbar and preventing withdrawal of the conductor from the housing.
The pressing of the conductor into the busbar, of course, requires a stable structure for resisting the compressive force of the spring finger. While firm support for the busbar can be provided either by the spring member or the housing, or both, a problem can arise when the connector is used with stranded wire. Stranded wire tends to flatten out or splay when subjected to the compressive force of the spring finger. Since the compressive and resistive forces of the spring finger are only created upon deflection of the spring finger, the splaying of the stranded wire reduces or even eliminates this deflection which can then defeat the dual purpose of the spring finger. The present invention addresses this problem.